Gravity interferometer system

ABSTRACT

A new type of gravity interferometer using an equilibrium fluid medium for its characteristic optical flatness is described. The technique consists of using the fluid surface to act as the sensing element for monitoring the direction of force gradients, since a sufficiently static and isolated fluid element does not exhibit any shear. One common example of this is the flat surface which a basin like container or fluid assumes when it is placed upon the earth. Such a surface is perpendicular to the vertical, that is, at right angles to the gradient of the earth&#39;&#39;s gravitational potential field. The new system includes a modification of the well known Michelson Interferometer. When complete and in operation the instrument indicates, over time, the very minute tilt angles of the earth&#39;&#39;s land mass in terms of a visible and measurable fringe pattern shift. These small land mass tilt angles, in turn, substantiate the predication of the tidal effects on the earth&#39;&#39;s land mass that are caused, primarily, by both solar and lunar gravitational attraction. The new instrument possesses a high degree of resolution. Matters related to mechanical and thermal considerations are discussed. Also, information is presented for an optional method of electronically monitoring and recording the instruments data, as signal output. Local noise is well dampened by the use of the fluid medium. The geophysical theory involved is developed and summarized. The latter agrees with the empirical, or with the results obtained from continuous operation of the new gravity interferometer system.

" tit ed States aterit [191 Bruce GRAVITY INTERFEROMETER SYSTEM {76]inventor: Marshall H. Bruce, P.O. Box 331,

Bedford, Mass. 01730 22 Filed: Mar. 26, 1970 21 Appl.No.:22,872

Primary ExaminerRonald L. Wibert Assistant Examiner-Conrad Clark [5 7]ABSTRACT A new type of gravity interferometer using an equilibrium fluidmedium for its characteristic optical flatness is described. Thetechnique consists of using the fluid surface to act as the sensingelement for monitoring the direction of force gradients, since asufiiciently static and isolated fluid element does not exhibit anyshear. One common example of this is the flat surface which a basin likecontainer or fluid assumes when it is placed upon the earth. Such asurface is perpendicular to the vertical, that is, at right angles tothe gradient of the earth's gravitational potential field. The newsystem includes a modification of the well known Michelsonlnterferometer. When complete and in operation the instrument indicates,over time, the very minute tilt angles of the earth's land mass in termsof a visible and measurable fringe pattern shift. These small land masstilt angles, in turn, substantiate the predication of the tidal effectson the earths land mass that are caused, primarily, by both solar andlunar gravitational attraction. The new instrument possesses a highdegree of resolution. Matters related to mechanical and thermalconsiderations are discussed. Also, information is presented for anoptional method of electronically monitoring and recording theinstruments data, as signal output. Local noise is well dampened by theuse of the fluid medium. The geophysical theory involved is developedand summarized. The latter agrees with the empirical, or with theresults obtained from continuous operation of the new gravityinterferometer system.

2 Claims, 7 Drawing Figures LOC.

Patented July 10, 1973 3,744,909

5 Sheets-Sheet l LOC,

INVENIOR M Hy SELF W TNE S 'ZIGNATUR Patented July 10, 1973 5Sheets-Sheet 2 W'i' N Hi5 TO SLGNA'I' UI m S W A Patented July 10, 19733,144,909

5 Sheets-Sheet 4 pw l I Ma NKSS TO SIGNATUREI Hy Sillli" Patented July10, 1973 5 Sheets-Sheet 5 LEGEND:

SYMBOL DEFINITION SYMBOL DEFINITION 1 A INSTRUWENT AT THE 1: 0czzocmz'rmc ANGLE at 1- B INSTRUMENT A'I TIME, t +At e caocmwmc ANGLE atAt+t c c 0mm MASS TIDAL CRES'IS P SUIZSOLAR or susumnn POINT DISTANCEBETWEEN CENTERS of MASSES n RADIUS of EARTH z NOR'IIX-LA'II'IUDINALSECTION of EARTH s DIRECTION of ROTATION 0 CENTER of EARTH At TIMEINTERVAL,ang1e-9 --9 o CENTER 0! SOLAR 9 011 LUNAR mss u t TIME g LMINVENTOR W fiw ITNE s TO s IGNATuRE By SELF GRAVITY ENTERFIERUMETERSYSTEM My invention relates to improvements in gravity metering devicesand more particularly to a gravityinterferometer system having anextreme degree of high resolution.

The objects of my invention are to produce a most effective and a mostsensitive gravity-inteferometer system having as an integral part of itsoptical system, a pair of interconnectd and intercommunicative fluidequilibrium reference optical flats of an order of excellence which,heretofore, has not been attained or used in the state of the art.

These and other objects will present themselves and become apparent frommy specifications, and the appended drawings as a part thereof, in whichH6. 1 is a plan view of the gravity-inteferometer systern and indicatesthe optics of the system;

H6. 2 is an elevation view of the gravityinterferometer system, drawnpartly in section through reference line lll of FIG. 1., to illustratethe configuration of the gravity-interferometer system;

FIGS. 3A, 3B, and 3C are three views of one of the support units foreach of the optical solid-state components of the gravity-interferometersystem;

FIG. 4 is a schematic drawing of one arrangement of thegravity-interferometer system and its accessory apparatus andinstrumentation as may be used to develop the high resolution signaloutput fringe pattern, with the upper portion of the shrouding enclosureremoved; and,

FIG. 5 is a reference sketch, geometric and symbolic of character;having no scale, but purporting to presout, by the use of greatmagnification of the true proportions that actually do exist, (e.g. anexaggerated scaie), one scientific use for the gravity-interferometer ofthe present invention. This sketch also includes a legend of symbols andtheir respective definitions as used both on the sketch and in thetechnical text that is a part of this specification.

The gravity-interferometer system comprises a pair of silica-glasscylindrically shaped cups, or resevoirs 6. The two cups 6 are separatedas to their respective positioning by a known, a certain, and measureddistance, and are provided with a tubular interconnecting andintercommunicating member '7 which adjoins the pair of cups 6 at, ornear, their respective lower lateral sides, respectively, as side-arms.The tublar member 7 is also made of silica-glass and therefore itbecomes an integral part of the two separated cup members by simpleglassblowing technique. The two resevoir cup members 6 and theirinterconnecting tubular member 7 are provided with a fluid fill 8. Thefill-point of the fluid fill 8 is somewhat less than brimful. Thisnecessitates a relative position for the two adjoined cup resevoirmemhers and their interconnecting tubular member, or members 6 and 7,respectively. A well matched pair of elipticlly shaped front-surfacereflectors, or mirrors, 9, having an excellent optical quality withrespect to their respective flatness, (for example, flat to withinonetwentieth of one wavelength of light), are positioned and held, eachone respectively, centrally located above each of the two fluid pools 8,and each one, respectively, is equidistantly located above each of thetwo fluid pool members, 8, respectively. A primary beam-splitter member10 is provided and is located precisely midway between the two elipticfront surface reflector members 9, and the central area of theirrespective fluid pools, 8, located below. Support members ill areprovided to hold and to adjust each of the several solid-state opticalcomponents of my gravityinterferometer. These supporting members, ill,have a sub-micrometric positive adjustment, inherent to their uniquedesign and structure: all of the support members llll are flanged at 12to form and provide a firm base, and each support member lll is providedwith an inner tee-shaped member 32 ring-sealed at 33, to memeber ill;and having its side-arm extension portion of its tee-shaped inner member32 protruding and extending outwardly, as passing through hole as thatis glassblown through the side of each outer support member 1111.Adjustments, for the rotation about the x,y, and z axes, are provided inthe form of end caps l3, which are drilled and tapped at three points,circumferentially, apart at 34, and adjustment fine-thread machinescrews, M, are used and are threaded into the tapped holes 343 to attainthe critical and very fine adjustments of the optical componentsfastened to sidearms 32, thusly supported. (Note: 1 have used d-80,threads on these adjustment end-cap screws. With relative case, it hasbeen possible to move the supported optial component with positivecontrol to the minute distance of Ml and even 10 centimeters hence, theprior term sub-micrometric.) Optional, and sometimes necessary, andsimilarly supported when used, is a secondary beam-splitter l5, and itis provided and is identical in optical character to the primarybeam-splitter member w. This secondary beam-splitter member 15 may beconsidered as a compensating optical component in the optical system ofthe gravityinterferometer system. Flanged base member E2 of each supportmember 111 is made secure, in an adhesive manner, upon a graphite (slab)member 116. it is to be noted that slab graphite member 116, asprovided, is tooled to a uniform thickness, and additionally is groundand lapped to a moderate degree of flatness on both its upper and lowerfaces; also, that it is shaped, drilled, and recessed with a groove toreceive and hold the two cup resevoir members 813 and theirinterconnecting tubular member 7 containing the fluid media 8.

The members thus far described in the foregoing, and given theirrespective specification identification numbers; or, namely, members athrough 16, also, members 32, 33, and 34 respectively, are the basicsimple items that are required to set up the typical and well knownMichelson type of light interferometer system. Certain painstakingoptical and geometric adjustments are, of course, required. Howeverassiduous this may be, the use of the fluid pools in their state ofequilibrium, facilitates these adjustments, and it is to be pointed outthat their use is a modification which is quite novel and unique' Whenused properly, the equilibrium fluid flats will function successfully asthe means of actually observing and of measuring the relativelyinfinitesimal rise and fall of the land mass, or earth itself. These infinitesimal land mass crests, or drops, are tidal of character. Theirmagnitude, for a one-meter gravityinterferometer system such as myinvention, is in the order of (approximately) a single fringe of light,(or the mercury green line 5,461 AN.) Obviously, to make use of thegravity-interferometer system as thus far described and specified, it isnecessary to provide a light source, located at E7. The beam of thislight, at 17, passing through the optical system of mygravityinterferometcr system will furnish a well defined fringe patternof high resolution upon a suitable screen member which may be used andlocated at 18; or, alternately, this screen location may also beconsidered as the location of the exit signal (fringe pattern) and befed from that point, or directed, into a more elaborate andsophisticated set of electronics. This latter method can provide meansof recording the signal fringe pattern data, over time. An insulatingshroud hood member 19 is constructed and encompasses the entireapparatus. The shroud member 19 is formed so as to provide means ofmaintaining a very close temperature level throughout the entiregravity-interferometer system, the light source provided and located at17, is also provided with a suitable housing with a collimating lensgroup 20. Optionally, this collimating lens group may include a lightfilter at some optimum wavelength. When used to detect and measure theland mass tidal rise and fall, at the locale of thegravity-interferometer system, the latter is directed toward east. Inorder that we may later be able to either make use of a known referencesignal, or make use of the complementary light signal fringe patternwhich exits back out of the entrance location, the followingparaphernalia is required and provided: (Note; these items are to beconsidered as accessary equipment, both optical and mechanical, to thegravity-interferometer system itself.) A simple beam-splitter 21 isprovided and is positioned across the path of the source beam fromlocation 17; a chopper-disc 22, and its drive motor 23; a pair offrontsurface plano reflector members 24 and 25 respectively; a secondsimple beam-splitter 26, and a photomultiplier detector tube 27. Thislatter detector, 27, requires an amplifier of the high-voltage type, aslocated at 28, have a signal recorder 29. The temperature within theconfines of the shroud member 19, which represents the ambientgravity-interferometer systems operating temperature, is monitored andrecorded; first by the sensor at 30, and its recording unit 31. Thelatter may be located remote from the apparatus, if desired. Atransducer element 35, having electrical terminals 37, is provided andit is used as an integral part of the axially extended inner tee-shapedsupport member 32, contained in the main support member 11,specifically, on that support member which holds the primarybeam-splitter 10. Very delicately controlled voltage, as provided bypower supply unit 36, having a feed-back as part of its circuit design,is fed to the transducer element 35, imparting a sub-micrometric controlmotion, axially; and, since the knowledge that the feed-back portion ofthe circuit gets is directly received from a minute change in the signaloutput fringe pattern, or a minute shift," the position of the primarybeamsplitter 10, having been preset, can be maintained to an extremeclose degree of arrest. Hence, when this trans ducer element 35 is inoperation, the change of voltage in the feedback part of the circuitwill be acceptable signal data, and will be recorded as such, over time.

For the materials having optimum characteristics for their respectivepurpose and use, I have chosen the following in the development of mygravityinterferometer system: Quartz (fused silica) for both the primaryand the secondary beam-splitters. Quartz for the pair of elipticalshaped reflectors; boro-silica glass for the oil pool cups (resevoirs)and their interconnecting tube, also for the support members. Graphiteplate comprises the base member. Careful and minimum amounts of epoxy(film) is used to render a reliable adhesion medium or bonding; and,boro-silica for reservoir cups and their adjoining intercommunicationtube. For the fluid pools, or the reference flats of equilibrium fluidcontained in the cups and their interconnecting tube there is a choiceof many fluids. When local conditions preclude both air-home and groundnoise it is very desirable to ue pure mercury. In most cases, sincethere is local traffic, and air travel, I have found that a petroleumbase oil, a moderate to low viscosity is very successful; it dampens thenoise at the same time assuming an extreme flat surface. On the otherhand, even distilled water may be used.

Experimental efforts, by others, have been made to measure the land mass(earth) tidal effects as are accepted, generally, as being attributableto both solar and lunar attraction. These prior efforts were less thansuccessful; however, they did furnish evidence of the forces in apositive manner. One purely theoretical calculation has presented anapproximation, numerically, of the land mass crest value of 30centimeters about 1 foot.

The device of the present invention, namely the gravity-interferometersystem, functions successfully. in order to explain how it works, andwhy it is a successful means of the measurement of the land mass tidaleffects, I will first use simple layman language; this appears quiteseemly at this point: The gravityinterferometer system may be consideredas divided into two states. Were one to assume an imaginary plane,horizontal and level, as separating the upper portion of the instrumentfrom its lower portion or, for example, a plane cutting across the topface of the graphite slab member (See Ref line 1l, of FIG. 1.) it wouldbe observed that the upper set of optical components are of solid-statecharacter; and, that the lower optical components are fluid-statecharacter. The former components, the solid-state, will follow whatevertilt that the land mass may assume; whereas the fluid-state opticalcomponents will constantly seek out and maintain its own equilibrium. It

now becomes apparent,therefore that the device at hand is to beconsidered as extremely sensitive by reason of the fact that theslightest rise or fall of the land mass, over some time period, willassume an angular deviation which, in turn, will impose asub-micrometric optical path length change to the interferometric systemof my type of gravity-interferometer system. This path length changewill be evidenced by a change in the signal output fringe pattern; andthis change is measureable. Thusly, the theoretical calculation referredto in the above is fully confirmed, or is corrected.

1 now depart from simple layman terminology and present a more technicalreview to summarize the principles of physics which are involved in boththe design and the operation of my type of gravity-interferometersystem; especially pointing out the need for the extreme sensitivity, asattained, by/for employing exacting sub-micrometric measurements offluid equilibrium: In the gravitational field of the rotating earth,withlunar and solar tidal influences, a fluid will assume an equilibriumsurface described by the equation:-

CONSTANT =-V(R, 5, 0) mam cos (b 3/2) is cos 0,,1 (G M W/D 3/2 is cos8,} Gran n3 The first term is the potential due to the earths mass (thatis, the line integral of the unit mass weight g (R, 6, The second termis the latitude dependence on the rotating earth with angular velocity(u, and, the third and fourth terms, respectively, are the lunar and thesolar potentials with geocentric angles 6 0,, masses M,,,, M, and themass center distance to earth center D,,,, D,, respectively.

it is easily seen that the temporal effects of the moon motion, forexample, cause a deviation of a potential line with a change ofgeocentric angle of:

Thus, if the deviation of a fluid were measured over a surface distanceof ds R d 9, then, since for the moon:

M /M 1/81 R /D,,, g 1/60 EB EB aR 1.25 X l" sin 2 dds.

if a surface distance of one meter were used, then the maximum value ofdr would be 1,250 A., or one-fourth the wavelength of the green line onmercury (5,461 A.) per meter of fluid extension. This may be calledlongitude position of the surface direction and it exhibits familiartidal phenomena. By measuring this displacement with an interferometer,it is possible to exceed the performance of the best of gravity metersemploying, as they do, such devices as restoring springs possessinginertial masses. The absence of major problems of drift and temperaturecompensation is especially attractive for an instrument of the typewhich i have illustrated in may several drawings, or lFlG. 1, throughHG. 3, inclusive.

There are, of course, other methods of this measurement which areconsidered (by self) as less sensitive and less reliable than theinterferometric method which i specify; for examples, first, themeasurement of the capacitance with the fluid becoming one plate of thecapacitor circuit; secondly, the use of an optical-lever device which,howsoever, must have an indicated capability of the measurements ofdistance of an order of X Ill centimeters, approximately equal to it)"fringes of visible light. in actual practice, however, i am justified inmy choice of the interferometric method, as being both reliable andpractical.

When the surface direction is changed so that (is Iihd b is the surfacedistance, then:

aiR/ds A: MR a; sin 2a; (R a; 8, b).

F-4 The displacement for normal" gravity is about 0.17 centimeters permeter of fluid extension, at a latitude of 45. This may be called thelatitude position of the surface direction and allows a directmeasurement of the ratio of the local gravitation to the distance fromthe earths axis. An instrument, which employs this principle, requirescomparison, astronomically, between the local zenith angle and theequilibrium angle of the fluid in the latitude position. When oneemploys an interferometer to measure the deviation of the fluid surfacefrom a sphere, the precision of fringe measure ment becomes thecriterion for the lower limit of mass detection. The interferometer isadjusted so that a detector is looking at a gray field, hence smallchanges in path length produce a direct and proportional change in thelight intensity monitored by the detector. The signal to-noise ratiodepends on the throughput of the interferometer, the light intensity atthe photomultiplier, the sensitivity of the detector unit, and themodulation efficiency.

Reference drawing H6. 4., indicates that a photomultiplier alternatelyreceives light through a chopper from the gray field fringe pattern;first, from the ordinary fringes exiting at the rear of theinterferometer; and, then, secondly, from the complementary fringesexiting from the input of the interferometer. This signal is thentime-shared by a locl -in amplifier which takes the difference betweenthese two signals, amplifies it, and drives a transducer which is anintegral part of the primary beam-splitter support (axially) to null thedifference via a feed-back circuit. The driving voltage to thetransducer is recorded to indicate the total fringe shift, over the timeperiod of a full tidal-cycle.

The total environment of my gravity-interferometer system is containedin a thermal enclosure, or a shroud, which maintains the temperature toa few-hundredths of one degree Centigrade Scale. This is consideredadequate since the instrument is equal arm length and it is constructedof low expansion graphite which quickly comes to uniform temperature dueto its high heat conductivity, Too, the equilibrium fluid oil poolspromptly adjust to a thermal change by reason of an equal expansion inboth arms; this is not detectable. The moderately viscous oil acts veryeffectively as a dampener with respect to airborne and ground-bornevibration. The oil maintains an optical surface which is sufficientlyflat for extreme sensitivity. The inherent problems of the gravitymeters in prior state of the art devices, those problems (as mentionedabove) of temperature drift, and the relaxation of mechanical spring orbeam elements, limited their use and their accuracy.

The stated use of my gravity-interferometer system as a means ofmeasuring the tidal deformation of the solid earth, in turn, couldcomplement Seismological studies and be related to new data as to thecomposition of the interior of the earth. indeed, by carefully analyzingthe response to my gravity-interferometer system to lunarsolargravitation it is now to be quite possible to assign an upper limit tothe ahsorbtion of gravitation, by noting that in part of the revolutionof the earth these bodies must be detected through the intervening massof the earth.

The generation of gravitational waves by stellar collapse in a novastage, or by intergalactic matterantimatter collisions has beenpredicted by a number of eminent theoretical physicists. Such wavescould conceivably excite the natural mode of the spherically shapedearth and set up oscillations which would be detected as changes inleveling, such as can be registered or detected with thegravity-interferometer system.

Finally, it is well known to the art that the Michelson type ofinterferometer will always produce or develop a bull 's-eye fringepattern, and that the closer to perfect and equal ray path-length onboth sides (legs) of the primary beam-splitter from each of the twointerfering flats, respectively, the larger the size of the central andcircular fringe of that same bulls-eye. Therefore, with high qualityoptics, little difficulty is to be experienced in attaining a relativelymassive central solid light fringe. Hence, the user of the device of thepresent invention, the gravity-interferometer system, has a wide scopeof choice in the operation of the instrument. A relatively coarseadjustment will furnish several, or but few, fringes in the signalfringe pattern (output). These can be rendered visible, if desired, upona suitable screen material at the outlet location, and the fringe shiftactually be observed, and actually counted over a given time interval.Alternately, excellent interferometric adjustment resulting in themassive central light fringe, can be used to measure and record thelight intensity output change over a similar time interval. The lattermethod may be preferred. It has certainly evidenced and made it possibleto attain resolution accuracies of an order of a few-hundredths of onelight fringe, repeatedly, and with accuracy.

Having thus described my invention in the above specification, and notwishing to depart from the true purposes and true principles of myinvention, I feel free to modify and better my novelty as improvedmaterials may become available; and that which I claim as new and usefuland desire to secure by Letters Patent is covered in the followingclaims:

1. A gravity interferometer system comprising a light source producing acoherent collimated beam path; a pair of uniformly shaped rightcylindrical reservoir cup members, said reservoir cup members positionedin a relatively level manner and separated by a fixed and predetermineddistance; an interconnecting tubular member as extending from the lowerside portion of one of the aforesaid cup members and adjoining the lowerside portion of the aforesaid second cup member, said tubular memberpresenting an intercommunicating free passage between both of theaforesaid reservoir cup members; an equilibrium fluid medium of aquantity sufficient to substantially fill the aforesaid pair ofreservoir cup members and their aforesaid interconnecting tubularmember, the equilibrium fluid medium creating an essentially opticallyflat surface within the said cup members; two eliptically shaped flatfront surface reflector members positioned equidistantly and centrallyabove the aforesaid two reservoir cup members, and each of saidreflectors supported at an angle of forty-five degress with respect tothe axes of the said reservoir cup members; a primary beamsplittermember positioned in said beam path such that a partial beam will bedirected to each of said eliptically shaped reflectors, from which thesaid partial beams will be reflected downward to the top flat centralportion of the aforesaid fluid medium in both of the said reservoircups; a return of the aforesaid partial beams reflected upwardly fromthe top central portion of said fluid surfaces, then reflected from eachof the aforesaid eliptically shaped reflectors, the two partial beamsredirected back to the aforesaid primary beamsplitter; lightinterference development at said primary beamsplitter, as a recombinedset of the aforesaid partial beams, said light interference of saidrecombined partial beams continuing onward from the said beamsplitterand exiting from the interferometer as signal output in. a visiblefringe pattern at the exit of said interferometer; a secondarybeamsplitter, or a compensator, positioned in the partial beam pathbeyond the aforesaid primary beamsplitter from the said light sourcebeam, said compensator equalizing the optical path length for theaforesaid set of partial beams in the light interference framing portionof the interferometer system; support members for each, respectively, ofthe aforesaid solidstate optical components,or, the two aforesaideliptically shaped front surface reflector members, the aforesaidprimary beamsplitter member, and the aforesaid secondary compensatorbeamsplitter member; a flanged base portion to each of said supportmembers; an inner tee-shaped tubular member located coaxially andringsealed within each of the aforesaid support members, said innertee-shaped tubular member having its side-arm thereof protruding throughside holes provided through the side of each of the said supportmembers; end cap members fastened over the end of each of the aforesaidsupport members, said end caps drilled and tapped to providethrough-holes spaced equidistantly in a circumferential manner about theouter surface of each of the said end cap members; fine threadedadjusting machine screws inserted into the said drilled and tappedthrough-holes to engage with the aforesaid inner tubular tee-shapedmembers of the said support members, said screws providing a fineadjustment of the positioning of the said inner tubular member; atransducer to provide sub-micrometric motion to the primarybeamsplitter; an exit location in the output path of the aforesaidrecombined partial beams, said exit location for either the visibleobservation of the said fringe pattern shift, over time, or for thepositioning of a photo-sensitive detector device to electronicallyobserve and record the same said light interference fringe patternshift, over time; a deliberate adjustment and optical alignment of theaforesaid interferometer system to obtain one given and well defined andrecorded fringe pattern observing and recording the time of day; ashrouding member to enclosed the entire gravity interferometer system;maintenance of a relatively close ambient temperature within theconfines of the aforesaid shrouding member; a monitoring of theaforesaid light interference fringe pattern shift over an extended timeinterval, and inclusive of the recording of said fringe pattern shift interms of single fringes, or fractions thereof; and, correlating theresults of these data to calculate the angle of the earths land masstilt angle, said tilt angles sine, in effect, being directlyproportional to the earths land mass tidal rise, or fall.

2. A gravity interferometer system comprised essentially the same as setforth in claim 1 but having provisions for an alternate method of signaloutput measurement, said method necessitating auxiliary components ofoptical, mechanical, and electronic character, or, a simple beamsplittermember positioned across the path of the aforesaid coherent collimatedlight source beam; a pair of flat front surface reflector members; achopper-disc and its synchronous electric motor drive assembly; a secondsimple beamsplitter member; a photomultiplier detector tube; anamplifier of high voltage type for the aforesaid photomultiplierdetector tube member; a thermocouple junction sensor and its calibratedmeter; a recorder to monitor the temperature, as connected to the saidthermocouple member; a transducer member, or the aforesaid devicemounted on the said main beamsplitter; a power supply having a feed-backas part of its circuitry to controll the aforesaid transducer device; arecorder to record the said feedback voltages, over time; a deliberateadjustment of all of the aforesaid auxiliary optical components,

llill pattern creating a gray field of light signal, said gray field oflight will not vary with the fringe pattern shift, over time, theaforesaid transducer device holding the gray field of light; and, theevalutation of the feed-back voltages, over time, presenting signal datafrom which the calculation of the earths land mass tilt angle can beobtained.

1. A gravity interferometer system comprising a light source producing acoherent collimated beam path; a pair of uniformly shaped rightcylindrical reservoir cup members, said reservoir cup members positionedin a relatively level manner and separated by a fixed and predetermineddistance; an interconnecting tubular member as extending from the lowerside portion of one of the aforesaid cup members and adjoining the lowerside portion of the aforesaid second cup member, said tubular memberpresenting an intercommunicating free passage between both of theaforesaid reservoir cup members; an equilibrium fluid medium of aquantity sufficient to substantially fill the aforesaid pair ofreservoir cup members and their aforesaid interconnecting tubularmember, the equilibrium fluid medium creating an essentially opticallyflat surface within the said cup members; two eliptically shaped flatfront surface reflector members positioned equidistantly and centrallyabove the aforesaid two reservoir cup members, and each of saidreflectors supported at an angle of forty-five degrees with respect tothe axes of the said reservoir cup members; a primary beamsplittermember positioned in said beam path such that a partial beam will bedirected to each of said eliptically shaped reflectors, from which thesaid partial beams will be reflected downward to the top flat centralportion of the aforesaid fluid medium in both of the said reservoircups; a return of the aforesaid partial beams reflected upwardly fromthe top central portion of said fluid surfaces, then reflected from eachof the aforesaid eliptically shaped reflectors, the two partial beamsredirected back to the aforesaid primary beamsplitter; lightinterference development at said primary beamsplitter, as a recombinedset of the aforesaid partial beams, said light interference of saidrecombined partial beams continuing onward from the said beamsplitterand exiting from the interferometer as signal output in a visible fringepattern at the exit of said interferometer; a secondary beamsplitter, ora compensator, positioned in the partial beam path beyond the aforesaidprimary beamsplitter from the said light source beam, said compensatorequalizing the optical path length for the aforesaid set of partialbeams in the light interference framing portion of the interferometersystem; support members for each, respectively, of the aforesaidsolid-state optical components, or, the two aforesaid eliptically shapedfront surface reflector members, the aforesaid primary beamsplittermember, and the aforesaid secondary compensator beamsplitter member; aflanged base portion to each of said support members; an innertee-shaped tubular member located coaxially and ringsealed within eachof the aforesaid support members, said inner tee-shaped tubular memberhaving its side-arm thereof protruding through side holes providedthrough the side of each of the said support members; end cap membersfastened over the end of each of the aforesaid support members, said endcaps drilled and tapped to provide through-holes spaced equidistantly ina circumferential manner about the outer surface of each of the said endcap members; fine threaded adjusting machine screws inserted into thesaid drilled and tapped through-holes to engage with the aforesaid innertubular tee-shaped members of the said support members, said screwsproviding a fine adjustment of the positioning of the said inner tubularmember; a transducer to provide sub-micrometrIc motion to the primarybeamsplitter; an exit location in the output path of the aforesaidrecombined partial beams, said exit location for either the visibleobservation of the said fringe pattern shift, over time, or for thepositioning of a photosensitive detector device to electronicallyobserve and record the same said light interference fringe patternshift, over time; a deliberate adjustment and optical alignment of theaforesaid interferometer system to obtain one given and well defined andrecorded fringe pattern - observing and recording the time of day; ashrouding member to enclosed the entire gravity interferometer system;maintenance of a relatively close ambient temperature within theconfines of the aforesaid shrouding member; a monitoring of theaforesaid light interference fringe pattern shift over an extended timeinterval, and inclusive of the recording of said fringe pattern shift interms of single fringes, or fractions thereof; and, correlating theresults of these data to calculate the angle of the earth''s land masstilt angle, said tilt angle''s sine, in effect, being directlyproportional to the earth''s land mass tidal rise, or fall.
 2. A gravityinterferometer system comprised essentially the same as set forth inclaim 1 but having provisions for an alternate method of signal outputmeasurement, said method necessitating auxilliary components of optical,mechanical, and electronic character, or, - a simple beamsplitter memberpositioned across the path of the aforesaid coherent collimated lightsource beam; a pair of flat front surface reflector members; achopper-disc and its synchronous electric motor drive assembly; a secondsimple beamsplitter member; a photomultiplier detector tube; anamplifier of high voltage type for the aforesaid photomultiplierdetector tube member; a thermocouple junction sensor and its calibratedmeter; a recorder to monitor the temperature, as connected to the saidthermocouple member; a transducer member, or the aforesaid devicemounted on the said main beamsplitter; a power supply having a feed-backas part of its circuitry to controll the aforesaid transducer device; arecorder to record the said feed-back voltages, over time; a deliberateadjustment of all of the aforesaid auxilliary optical components, saidadjustments and said alignments resulting in the pick up of thecomplementary light interference fringe pattern which issues back towardthe aforesaid light source beam, and redirect this secondary, orcomplementary light interference fringe pattern through the aforesaidchopper disc and then on to the said detector tube member; thecomplementary fringe pattern added to the aforesaid primary output lightinterference fringe pattern creating a gray field of light signal, saidgray field of light will not vary with the fringe pattern shift, overtime, the aforesaid transducer device holding the gray field of light;and, the evaluation of the feed-back voltages, over time, presentingsignal data from which the calculation of the earth''s land mass tiltangle can be obtained.